Vitamin B12 for Nutritional Deficiency Hair Loss
FBased on 19 studies (1 RCT) with 8,130 total participants. Results are mixed across studies.
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F
The Bottom Line
Research shows mixed results for vitamin B12 and hair loss — while deficiency may contribute to hair thinning, supplementation is unlikely to help unless you have a confirmed B12 deficiency.
- Mixed results across 20 studies — no consistent benefit from supplementation
- Some studies find lower B12 levels in hair loss patients, others do not
- No large-scale RCTs testing B12 supplementation specifically for hair regrowth
- Supplementation may only help if a genuine B12 deficiency is present
Key Study Findings
retrospective observational
n=113
Telogen Effluvium Following Coronavirus Disease-2019 Infection: A Retrospective Study of 113 Cases.
Dose: None
vs: Placebo
Effect: None
None
Retrospective cohort
n=2851
Retrospective Review of 2851 Female Patients With Telogen Effluvium: A Single-Center Experience.
Dose: None
vs: Placebo
Effect: Ferritin low in 46.5% of patients; iron deficiency in 29.5%
p<0.05
Review
Medical Marijuana and Treatment Personalization: The Role of Genetics and Epigenetics in Response to THC …
Dose: None
vs: None
Outcome: None
Effect: None
None
Population: Review of pharmacogenomics of THC and CBD
case-control study
n=180
A comprehensive investigation of biochemical status in patients with telogen effluvium: Analysis of Hb, ferritin, …
Dose: not applicable
vs: Placebo
Effect: None
None
Cross-Sectional Study
n=108
Evaluation of the relationship of digital phototrichogram findings of patients with diffuse hair loss with …
Dose: None
vs: Placebo
Effect: None
0.05
Case-control
n=973
Micronutrient Deficiencies and Digital Computerized Phototrichogram Analysis in Telogen Effluvium: a Retrospective Correlation Study in …
Dose: None
vs: Placebo
Effect: r=0.417 (HGB and AHR in females)
p=0.008
Key Statistics
19
Studies
8130
Participants
↔
Mixed
F
Grade
Referenced Papers
Retrospective Review of 2851 Female Patients With Telogen Effluvium: A Single-Center Experience.
Other
Journal of cosmetic …
2025
4 citations
Genes
2025
1 citations
Telogen Effluvium Following Coronavirus Disease-2019 Infection: A Retrospective Study of 113 Cases.
Other
International journal of …
2025
Journal of cosmetic …
2024
7 citations
Northern clinics of …
2024
1 citations
JAMA
2023
49 citations
Dermatology practical & …
2023
4 citations
Sports medicine - …
2022
34 citations
Frontiers in pharmacology
2022
31 citations
Journal of cosmetic …
2022
22 citations
Turkish journal of …
2022
8 citations
Journal of pain …
2020
56 citations
NonScarring Diffuse Hair Loss in Women: a Clinico-Etiological Study from tertiary care center in North-West India.
Observational
Journal of cosmetic …
2019
25 citations
American journal of …
2017
104 citations
Journal of drugs …
2016
56 citations
Dermatology research and …
2016
26 citations
Acta dermatovenerologica Croatica …
2016
6 citations
Prostaglandins, leukotrienes, and …
2015
40 citations
Clinical and experimental …
2009
34 citations
Dermatologic clinics
1993
38 citations
Dosage & Usage
mg = milligrams · mcg = micrograms (1,000× smaller) · IU = International Units
Commonly Used Dosages
- general:
- 2.4 mcg/day
- deficiency:
- 1,000-2,000 mcg/day
Upper limit: No established UL
Dosages Studied in Research
| Dosage | Duration | Effect | N |
|---|---|---|---|
| None | -- | Neutral | 113 |
| None | -- | Neutral | 2851 |
| None | -- | Mixed | -- |
| not applicable | -- | Mixed | 180 |
| None | -- | Mixed | 108 |
| None | -- | Positive | 973 |
| None | -- | Neutral | -- |
| 300 mg single dose | -- | Mixed | 9 |
Best taken: With meals; sublingual form can be taken any time
Safety & Side Effects
Reported Side Effects
- ⚠ Generally well tolerated even at high doses
- ⚠ Rare allergic reactions (itching, swelling)
- ⚠ Mild diarrhea or nausea at very high doses
Known Interactions
- ● Metformin (reduces B12 absorption by 10-30%)
- ● Proton pump inhibitors and H2 blockers (reduce B12 absorption)
- ● Colchicine (may reduce B12 absorption)
Tolerable upper intake: No established UL
Always consult your healthcare provider before starting any supplement.
Frequently Asked Questions
Does Vitamin B12 help with Nutritional Deficiency Hair Loss?
Based on 19 studies with 8,130 participants, there is insufficient evidence at this time that Vitamin B12 may support Nutritional Deficiency Hair Loss management. Our evidence grade is F (Evidence Against).
How much Vitamin B12 should I take for Nutritional Deficiency Hair Loss?
Studies have used various dosages. A commonly studied range is 2.4 mcg/day. Always consult your healthcare provider before starting any supplement regimen.
Are there side effects of Vitamin B12?
Reported side effects may include Generally well tolerated even at high doses, Rare allergic reactions (itching, swelling), Mild diarrhea or nausea at very high doses. Most side effects are mild and dose-dependent. Consult your doctor if you experience any adverse reactions.
How strong is the evidence for Vitamin B12 and Nutritional Deficiency Hair Loss?
We rate the evidence as Grade F (Evidence Against). This rating is based on 19 peer-reviewed studies with 8,130 total participants. The overall direction of effect is mixed.
Related Evidence
Other ingredients for Nutritional Deficiency Hair Loss
Vitamin B12 for other conditions
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products and information on this website are not intended to diagnose, treat, cure, or prevent any disease. The evidence grades presented are based on our analysis of published peer-reviewed research and do not constitute medical advice. Always consult your healthcare provider before starting any supplement regimen.